It looks like your distro hasn’t associated JNLP files with the Java webstart binary. You should be able to figure that out with a little googling.
I have installed java 1.8.0_45(b14) version as it is pre-requisite for ignition 7.7.0
Yet not able to launch the designer.Each time on clicking launch designer, the designer.jnlp file opens.
Please help me to fix it.
Regards,
Pradnya